1. Field of the Invention
The present invention relates to an RFID tag and related operating methods, and more particularly, to an RFID integrated with an electronic device and related methods for anti-theft and data transmission purposes.
2. Description of the Prior Art
Radio frequency identification (RFID) techniques provide a non-contact automatic identification system capable of transmitting radio frequency (RF) signals between a reader and a tag in a wireless manner for object identification or data transmission purposes. RFID systems, characterized in wireless and bi-directional data transmission, long lifetime, high safety and high endurance, are particularly suitable for applications in automatic systems or harsh environments, such as in warehouse management, burglarproof security systems for automobiles, livestock identification, automatic charge systems, or quality control, etc.
An RFID system usually includes an RFID tag, a reader and a computer system. The RFID tag, having a chip and an antenna assembled using special packaging techniques, can store data and conduct data transmission with the RFID reader. The RFID tag usually includes an unique identifier (UID) and a memory space for data storage. For accurate data transmission, the RFID tag and the RFID reader have to communicate based on agreed-upon protocols, such as the communication frequency, the modulation type, the transmission speed or the transmission command. Therefore, when the RFID tag is located within the operational range of the RFID reader, the RFID reader can access the data stored in the RFID tag.
RFID tags can be categorized into active RFID tags and passive RFID tags. An active RFID tag, including a built-in battery, can automatically transmit data to an RFID reader using self-provided power and can perform internal system control using the built-in battery. As a result, active RFID tags are advantageous in longer effective sensing ranges, but disadvantageous in a shorter lifetime, larger sizes and higher costs. A passive RFID tag, without a built-in battery, receives RF signals from an RFID reader, transforms the RF signals into power for operating the passive RFID tag using an internal circuit, and then transmits data to the RFID reader. As a result, passive RFID tags are disadvantageous in shorter effective sensing ranges, but advantageous in a longer lifetime, smaller sizes and lower costs. Passive RFID tags are mainly used in short-distance applications, such as in entrance or traffic controls.
Reference is made to FIG. 1 for a functional block diagram illustrating a prior art RFID system 100. The RFID system 100 includes a passive RFID tag circuit 10 and an RFID reader 11. The RFID tag circuit 10 includes a rectifier 12, a power management module 13, a demodulator 14, a modulator 15, an oscillator 16, a digital baseband circuit 17, and a memory 18.
The RFID reader 11 outputs an RF signal SRF of a predetermined frequency using its antenna. When the RFID tag circuit 10 is located within the operational range of the antenna, the RFID tag circuit 10 can receive the RF signal SRF using its antenna. The rectifier 12 transforms the RF signal SRF into a directive current (DC) voltage VDD_REC and outputs the DC voltage VDD_REC to the power management module 13. The power management module 13, which can include a regulator, generates a corresponding DC voltage VDD for operating each device in the RFID tag circuit 10 stably. By demodulating the RF signal SRF, the demodulator 14 generates a corresponding demodulation signal SDEM for subsequent data processing. The oscillator 16 generates a clock signal SCLK for operating the digital baseband circuit 17. The demodulation signal SDEM includes address information of the data to be accessed by the RFID reader 11. Therefore, the digital baseband circuit 17 can access the data stored in the memory 18 based on the clock signal SCLK and the demodulation signal SDEM, and then outputs a corresponding data signal SDATA. The modulator 15 can modulate the data signal SDATA based on back scatter modulation so that data can be transmitted more effectively. In back scatter modulation, the modulator 15 adjusts its input impedance using the continuous carrier waves sent by the RFID reader 11, and the phases of the carrier waves reflected by the antenna of the RFID tag circuit 10 can thus be adjusted. Back scatter modulation provides the effects similar to phase-shift-keying (PSK) in which an RF signal SRF′ corresponding to the data signal SDATA can be generated and transmitted to the RFID reader 11 via the antenna of the RFID system 100.